I've been a traditional artist all my life but have lately been trying to expand my bag of tricks to include the digital medium. There is one thing about painting in photoshop that been bugging me and I hope someone here can help.

In the picture below using my Wacom tablet with the opacity pressure turned on I make a blend from the top of the page towards the bottom. I start out with life pressure on the pen and gradually increase the pressure as I near the middle and then get lighter again.(fig 2) No problem in this gradation of color.

Then (fig 3) I do the same thing but the problem is where the color overlaps it gets darker. (fig 1) I just want to add to my gradation.

Any suggestions?